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Ruthenium(II) polypyridyl complexes: synthesis, cytotoxicity in vitro, reactive oxygen species, mitochondrial membrane potential and cell cycle arrest studies
Transition Met Chem (2013) 38:765–770
DOI 10.1007/s11243-013-9747-z
Synthesis, crystal structures, and photoluminescence of two
silver(I) coordination polymers based on 2-sulfoterephthalic
acid and N-donor ligands
Jie Wang • Jia-Guo Wang • Xin-Hua Li •
Hong-Ping Xiao
Received: 11 May 2013 / Accepted: 28 June 2013 / Published online: 12 July 2013
Ó The Author(s) 2013. This article is published with open access at Springerlink.com
Abstract The reactions of 2-sulfoterephthalic acid
(H3stp) with silver nitrate in the presence of 2-aminopyrimidine (apym) or 2-amino-4,6-dimethylpyrimidine
(dapym) generated two 2-D coordination polymers
{[Ag3(stp)(apym)3]2H2O}n (1) and {[Ag2(Hstp)(dapym)2
(H2O)]H2O}n (2). The complexes have been characterized
by single-crystal X-ray diffraction, physico-chemical, and
spectroscopic methods. Both complexes have a 2-D layer
structure with infinite 1-D chains linked by stp3- ligands
and hydrogen bonds. The luminescent properties of the
complexes were investigated.
Introduction
Reasons for the current interest in the crystal engineering
of silver coordination polymers include their interesting
mechanisms of molecular self-assembly [1–3], abundant
weak interactions [4–6], potential applications in many
areas such as electrical conductivity [7], magnetism [8],
and catalysis [9] and so forth. Silver(I) atoms can accommodate a wide variety of stereochemistries, with coordination numbers of two to six and versatile coordination
geometries, including linear, T-shaped, square-planar, tetrahedral, square-pyramidal, trigonal-bipyramidal, and
octahedral [10–13]. Furthermore, Ag(I) with a d10 closedshell electronic configuration tends to form argentophilic
interactions, which have an important influence on the
formation of polymetallic clusters [14–16]. In particular,
J. Wang J.-G. Wang X.-H. Li H.-P. Xiao (&)
College of Chemistry and Materials Engineering, Wenzhou
University, Wenzhou 325035, People’s Republic of China
e-mail: jwwzedu@163.com
Ag(I) complexes with carboxylate ligands have been
widely investigated for their intriguing structural topologies and potential applications [17–20]. We selected
2-sulfoterephthalic acid as an organic ligand, based on the
following twofold considerations. First, the two carboxylate groups and one sulfonate group of the ligand could act
as bridging groups to form coordination polymers [21–24];
second, the protons of the ligand, if not all dissociated,
could form H-bonds with adjacent ligands or solvent
molecules [10, 25]. In addition, the introduction of N-donor
organic ligands is an important strategy for the construction
of novel coordination polymers [26–28].
Taking into account these considerations, and following
on from our previous work [29], we have studied the selfassembly of Ag(I) with H3stp and auxiliary N-donor
ligands. In this paper, we report the syntheses, crystal
structures, and properties of two new silver(I) coordination
polymers, namely {[Ag3(stp)(apym)3]2 H2O}n (1) and
{[Ag2(Hstp)(dapym)2(H2O)]H2O}n (2).
Experimental
Materials and instrumentation
All chemicals and solvents were obtained from commercial
sources as reagent grade and used without further purification in the syntheses. Elemental analyses for C, H, and N
were obtained with a CHN-O-Rapid Analyzer and an
Elemental Vario Microanalyzer. The infrared spectra were
taken on a Bruker Equinox 55 FTIR spectrometer as KBr
pellets in the 400–4,000/cm-1 region. The fluorescence
spectra were measured using a Shimadzu RF-7000 spectrometer on powdered samples in the solid state at room
temperature.
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766
Transition Met Chem (2013) 38:765–770
Synthesis of {[Ag3(stp)(apym)3]2H2O}n (1)
A solution of AgNO3 (0.0338 g, 0.20 mmol) in water
(10 ml) was added to a stirred solution of 2-sulfoterephthalic acid (0.0536 g, 0.20 mmol) and 2-aminopyrimidine
(0.019 g, 0.20 mmol) in DMF(5 ml). The mixture was
stirred for 10 min and then the precipitate was filtered off;
the filtrate was allowed to evaporate in the dark. After
2 weeks, colorless block-shaped crystals were obtained.
Yield 0.07 g (40 %). Anal. Calcd for C20H22Ag3N9O9S: C
27.1, H 2.5, N 14.2 %; Found: C 27.0, H 2.4, N 14.1 %;
FTIR (KBr pellet, cm-1) selected bands: m = 3,856 w,
3,740 w, 3,403 s, 3,314 s, 3,178 m, 1,577 s, 1,479 s,
1,360 s, 1,203 s, 1,072 m, 1,022 m, 799 m, 676 w, 621 m,
574 w, 508 m.
Synthesis of {[Ag2(Hstp)(dapym)2(H2O)]H2O}n (2)
A solution of AgNO3 (0.0338 g, 0.20 mmol) in water
(10 ml) was added to a stirred solution of 2-sulfoterephthalic acid (0.0536 g, 0.20 mmol) and 2-amino-4,6-dimethylpyrimidine (0.0246 g, 0.20 mmol) in a mixture of
DMF(5 ml) and CH3CN(5 ml). The mixture was stirred for
10 min and then the precipitate was filtered off; the filtrate
was allowed to evaporate in the dark. After 2 weeks, colorless sheet crystals were obtained. Yield 0.06 g (38 %).
Anal. Calcd for C20H26Ag2N6O9S: C 32.4, H 3.5, N
11.3 %; Found: C 32.3, H 3.5, N 11.3 %; FTIR (KBr
pellet, cm-1) selected bands: m = 3,856, 3,741 w, 3,508 m,
Table 1 Crystal data for complexes 1 and 2
Complex
1
2
Empirical formula
C20H22Ag3N9O9S
C20H26Ag2N6O9S
Mr
Crystal system
888.14
Triclinic
742.27
Monoclinic
Space group
P-1
P 21/c
a (Å)
8.4598(5)
9.8955(14)
b (Å)
8.7939(5)
22.883(3)
c (Å)
18.5836(11)
13.5489(13)
a (°)
80.2270(10)
90
b (°)
81.5540(10)
124.005(7)
c (°)
74.6730(10)
90
V (Å3)
1,306.41(13)
2,543.3(5)
Z
2
4
h range (°)
1.12–25.10
2.02–25.50
Dcalc(Mg m-3)
2.258
1.939
l(mm-1)
2.377
1.684
F(000)
868
1,480
R1 [I [ 2r]
wR2 (all data)
0.0287
0.0361
0.0308
0.0325
Ra1 = R||Fo| - |Fc||/RFo|. wRb2 = [Rw(F2o - F2c )2/Rw(F2o)]1/2
123
3,393 s, 3,213 m, 1,937 m, 1,647 s, 1,589 s, 1,475 m,
1,427 m, 1,372 s, 1,285 m, 1,223 s, 1,074 m, 1,023 m,
789 m, 728 w, 672 w, 624 m, 572 w, 496 m.
X-ray crystallographic study
The X-ray single-crystal data for complexes 1 and 2 were
recorded on a Brucker APEX II area detector diffractometer with graphite-monochromated MoKa radiation
(k = 0.71073 Å). Semi-empirical absorption corrections
were applied using the SADABS program. The structures
were solved by direct methods and refined by full-matrix
least squares on F2 using SHELXL-97. All non-hydrogen
atoms were refined anisotropically. The carboxyl and water
H atoms were located from difference Fourier maps; other
hydrogen atoms were placed in geometrically calculated
positions. Experimental details for X-ray data collection of
1 and 2 are presented in Table 1, and selected bond lengths
are listed in Table 2.
Results and discussion
Structure of complex 1
Single-crystal X-ray diffraction analysis reveals that
{[Ag3(stp)(apym)3]2H2O}n (1) presents a 2-D sheet based
on a 1-D double chain, which crystallizes in the space
group P-1. There are three Ag(I) atoms, one 2-stp ligand,
three apym ligands, and two lattice water molecules in the
asymmetric unit of 1. As depicted in Fig. 1a, three crystallographically different Ag(I) atoms are located in an
approximate T-shaped coordination geometry and coordinated by one oxygen from the same 2-stp ligand and two
nitrogen atoms from two different apym ligands. The
Ag–O bond distances vary from 2.283(3) to 2.509(3) Å,
and the Ag–N bond lengths range between 2.190(3) and
2.330(4) Å. Both Ag–O and Ag–N bond lengths are well
matched with those observed in similar complexes [10–14,
29].
The Ag(I) atoms are linked by bidentate apym ligands to
form 1-D zigzag chains in which the apym ligands are
oppositely arranged, and the stp ligands extend the 1-D
single chains into a 1-D double chain, containing classical
hydrogen bonds (Fig. 1c). Subsequently, with Ag2 as a
node, two pairs of reverse direction 1-D double chains link
adjacent sulfo group oxygen atoms (O3) from stp ligands
into a 2-D laminar framework (Fig. 1b). In addition, the
amino groups of apym ligands form hydrogen bonds with
the coordinated O5 of the carboxyl groups and water
molecules, while the water molecule form hydrogen bonds
with the coordinated O2 and O5 atoms of the carboxyl
groups (as depicted in Table 3).
Transition Met Chem (2013) 38:765–770
767
Table 2 Selected bond lengths (Å) angles (°) for complexes 1 and 2
{[Ag3(stp)(apym)3]2H2O}n (1)
Bond lengths (Å)
Ag(1)-O(1)
2.499(3)
Ag(1)-N(1)
2.206(3)
Ag(1)-N(9)#1
2.190(3)
Ag(2)-O(3)
2.509(3)
Ag(2)-N(7)
2.233(3)
Ag(3)-O(6)
2.283(3)
Ag(3)-N(3)#2
2.226(3)
Ag(3)-N(6)#3
2.330(4)
N(9)#1-Ag(1)-N(1)
157.91(12)
N(9)#1-Ag(1)-O(1)
98.97(12)
N(1)-Ag(1)-O(1)
102.85(12)
N(7)-Ag(2)-N(4)
153.11(13)
N(7)-Ag(2)-O(3)
97.28(11)
N(4)-Ag(2)-O(3)
108.11(11)
O(6)-Ag(3)-N(6)#3
98.35(12)
N(3)#2-Ag(3)-N(6)#3
124.68(12)
N(3)#2-Ag(3)-O(6)
132.10(12)
Bond angles (°)
Symmetry codes: #1(-x ? 2,-y ? 1,-z); #2(-x ? 2,-y,-z ? 1); #3(x, y -1, z)
{[Ag2(Hstp)(dapym)2(H2O)]H2O}n (2)
Bond lengths (Å)
Ag(1)-N(4)
2.200(3)
Ag(1)-N(1)
2.202(3)
Ag(1)-O(1)
2.494(2)
Ag(2)-O(8)
2.444(3)
Ag(2)-O(4)
2.715(6)
Ag(2)-N(2)#1
2.250(3)
Ag(2)-N(5)#2
Bond angles (°)
2.285(3)
N(4)-Ag(1)-N(1)
157.36(9)
N(1)-Ag(1)-O(1)
99.04(9)
N(4)-Ag(1)-O(1)
96.96(9)
O(8)-Ag(2)-O(4)
99.34(19)
N(2)#1-Ag(2)-O(8)
100.50(10)
N(5)#2-Ag(2)-O(8)
94.24(10)
N(2)#1-Ag(2)-O(4)
112.97(14)
N(5)#2-Ag(2)-O(4)
93.80(14)
N(2)#1-Ag(2)-N(5)#2
150.79(9)
Symmetry codes: #1(x,-y ? 3/2, z ? 1/2); #2(-x,-y ? 1,-z ? 1)
Fig. 1 a Asymmetric unit of {[Ag3(stp)(apym)3]2H2O}n (1) and
coordination environments around the Ag(I) atoms. Water molecules
and corresponding H atoms are omitted for clarity. b The 2-D laminar
structure in complex 1 based on the Ag(I) atoms, stp and apym
ligands along a 9 b 9 c plane. c View of the 1-D double chain in
complex 1 along the a axis
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768
Table 3 Hydrogen bonds for
complexes 1 and 2 (Å and °)
Transition Met Chem (2013) 38:765–770
d(D-H)
d(HA)
\(DHA)
d(DA)
N(8)-H(8B)O(8)
0.90
1.96
173.0
2.852(5)
N(8)-H(8A)O(5)#5
0.90
2.64
132.3
3.312(6)
N(8)-H(8A)O(9)#6
0.90
2.38
125.8
2.993(7)
N(5)-H(5B)O(1)
0.90
2.16
133.6
2.853(5)
N(5)-H(5A)O(6)#4
0.90
2.13
148.7
2.934(5)
N(2)-H(2B)O(7)
0.90
2.03
160.1
2.890(5)
N(2)-H(2A)O(1)
0.90
2.08
177.0
2.983(5)
O(9)-H(9C)O(2)#7
0.85
2.33
159.0
3.142(7)
O(8)-H(8E)O(4)
0.85
2.12
132.6
2.769(5)
O(8)-H(8C)O(2)#8
0.85
2.02
130.0
2.651(5)
D-HA
{[Ag3(stp)(apym)3]2H2O}n (1)
Symmetry codes: #4 x, y ? 1, z; #5 -x ? 2,-y,-z; #6 -x ? 1,-y ? 1,-z; #7 x-1,y ? 1, z; #8 x-1,y,z
{[Ag2(Hstp)(dapym)2(H2O)]H2O}n (2)
N(6)-H(6B)O(1)
0.86
2.39
136.3
3.072(4)
N(6)-H(6B)O(3)
N(6)-H(6B)O(30 )
0.86
0.86
2.33
2.09
138.5
139.6
3.027(7)
2.802(7)
N(6)-H(6A)O(40 )#2
0.86
1.99
167.0
2.838(7)
N(6)-H(6A)O(4)#2
0.86
1.91
168.7
2.757(6)
N(3)-H(3B)O(1)
0.86
2.54
137.7
3.224(4)
N(3)-H(3A)O(8)#3
0.86
2.07
163.0
2.905(4)
O(9)-H(9C)N(4)#4
0.85
2.61
148.5
3.366(5)
O(9)-H(9B)O(3)#4
0.85
2.18
118.5
2.696(7)
O(8)-H(8C)O(9)
0.85
1.98
151.4
2.761(5)
O(8)-H(8B)O(2)
0.85
1.88
154.5
2.671(4)
O(7)-H(7)O(2)#6
0.82
2.65
128.2
3.221(4)
O(7)-H(7)O(1)#6
0.82
1.76
171.7
2.577(3)
Symmetry codes: #2-x,-y ? 1,-z ? 1; #3 x,-y ? 3/2, z-1/2; #4 -x ? 1, y ? 1/2,-z ? 1/2;
#6x ? 1,-y ? 3/2, z ? 1/2
Crystal structure of complex 2
The complex 2 crystallizes in the monoclinic P21/c space
group. The asymmetric unit of 2 contains two Ag(I) atoms,
one Hstp ligand, two dapym ligands, and one aqua ligand,
as well as one lattice water molecule. As illustrated in
Fig. 2a, the Ag1 adopts a T-shaped geometry completed by
one oxygen from the Hstp ligand and two nitrogen atoms
from different dapym ligands. The maximum angle around
Ag1 is 157.36(9) Å. Atom Ag2 is located in a distorted
tetrahedral geometry with one aqua ligand, one oxygen
atom from an Hstp ligand, and two nitrogen atoms from
two dapym ligands as donors. Each dapym ligand uses the
l2-g1:g1 bidentate coordination mode to bridge two adjacent Ag(I) atoms. As a consequence, the Ag(I) atoms are
extended by the dapym ligand spacers to afford a 1-D chain
almost along the [001] direction (Fig. 2c), within which the
distance between successive Ag(I) atoms is 6.142(9) Å.
The Hstp ligand acts as a linker to equip a 2-D layer
(Fig. 2b) by connecting two neighboring parallel
123
coordination chains through Ag–O coordination, as well as
intermolecular hydrogen bond interactions with the coordinated carboxylate and sulfo group oxygen atoms of Hstp
ligands, plus further H-bonding involving both coordinated
and guest water, as depicted in Table 3.
Thermogravimetric and photoluminescence analyses
Thermogravimetric (TG) analysis was performed under an
N2 atmosphere on crystalline samples of complexes 1 and 2
(Fig. 3a). The TG curve of 1 shows the first weight loss of
4.12 % in the temperature range 40–80 °C, associated with
the exclusion of two lattice water molecules (calcd
4.85 %); then, from 200 to 700 °C, the stp and apym
ligands are released in a featureless process, to give a
residue of Ag2SO4. Complex 2 starts to lose one lattice
water molecule in the temperature range 40–80 °C (obsd
1.74 %; calcd 2.02 %), and then, the curve shows further
decomposition in the temperature range 200–250 °C with a
Transition Met Chem (2013) 38:765–770
Fig. 2 a Asymmetric unit of {[Ag2(Hstp)(dapym)2(H2O)]H2O}n (2)
and coordination environments around the Ag(I) atoms. Water
molecules and corresponding H atoms are omitted for clarity. b 2-D
769
layer structure in complex 2 consisting of hydrogen bonds. c 1-D
metal-organic polymer based on the Ag(I) atoms and dapym ligands
Fig. 3 a TGA curves for
complexes 1 and 2. b The solidstate emission photoluminescent
spectra of 1 (kex = 390 nm), 2
(kex = 290 nm) and free H3stp
(kex = 321 nm) at room
temperature
20.00 % weight change, corresponding to loss of the dapym ligand (calcd 20.08 %). The third weight loss of
13.72 % (calcd 12.72 %) corresponds to the loss of the
Hstp ligands and one aqua ligand without a clear inflection.
The luminescence properties of both complexes and free
H3stp were studied in the solid state. As shown in Fig. 3b,
very similar emission bands were observed for the two
complexes, while emission of the free H3stp ligand with
kem = 437 nm (kex = 321 nm) was observed, which is
probably attributable to p* ? n or p* ? p transitions.
Compared to the spectrum of the free ligand, the emission
band of complex 1 is red-shifted by 15 nm. The shift can
be attributed to ligand to metal charge transfer (LMCT),
involving the filled p orbitals of coordinated N atoms and
the vacant 5 s orbitalof Ag(I), mixed with metal-centered
(d–s/d–p) transitions [30–32]. In contrast to complex 1, the
emission band of 2 is blue-shifted by more than 65 nm,
which could be assigned to p* ? p electronic transitions
of the ligand. The blue shift of the emission compared with
that of the free ligand may be attributed to coordination of
the ligand to Ag(I), enhancing its conformational rigidity
and decreasing the non-radiative energy loss [12].
123
770
Generally speaking, Ag(I) complexes emit weak photoluminescence at low temperature, owing to the intense spinorbital coupling of Ag(I) [12, 33, 34]. Consequently,
complexes 1 and 2 are unusual examples of room temperature luminescent Ag-containing polymers.
Conclusions
From the reactions of AgNO3, 2-sulfoisophthalic acid, and
N-donor ligands, we synthesized and structurally characterized two Ag(I) coordination complexes, in which the
auxiliary ligands are different. This investigation may
supply some new information for the design and crystal
engineering of such crystalline materials. In addition, these
complexes display modest thermal stability and solid-state
fluorescent emission. Further studies in this respect are
under way in our laboratory.
Supplementary material
CCDC 912814, 912815 contain the supplementary crystallographic data for complexes 1 and 2. These data can be
obtained free of charge from The Cambridge Crystallographic Data Centre via http://www.ccdc.cam.ac.uk/deposit
or from the Cambridge Crystallographic Data Centre, 12
Union Road, Cambridge CB2 1EZ, UK [Telephone: ?4401223-762910; Fax:?44-01223-336033; E-mail: deposit@
ccdc.cam.ac.uk].
Acknowledgments We gratefully acknowledge financial support of
this work by the Nation Natural Science Foundation of China (Grant
Nos. 21271143 and 21171133), the Opening Foundation of Zhejiang
Provincial Top Key Discipline (No. 100061200132).
Open Access This article is distributed under the terms of the
Creative Commons Attribution License which permits any use, distribution, and reproduction in any medium, provided the original
author(s) and the source are credited.
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